Question 1176374
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<pre>

Let E = Evan' scores

    R = the sum of scores of the 3 his friends.


Then you have this equation


    {{{(E + R)/4}}} = 80,   or   E + R = 320     (1)


and this equation


    {{{(99 + R)/4}}} = 86,   or  99 + R = 344    (2).



Subtract equation (1) from equation (2)


    99 - E = 24

    99 - 24 = E

     E      = 75.      <U>ANSWER</U>
</pre>

Solved.